P2Y1 receptors are linked to KCa2 channels in PC12 cells

Results In PC12 cells stably expressing rat P2Y1 receptors (PC12P2Y1), but not in wild type PC12 cells (PC12-wt), ADP induced rises in intracellular Ca2+ with half-maximal effects at 15 ± 1.3 μM. In whole-cell patch-clamp recordings, ADP inhibited ICa of PC12-P2Y1 cells (EC50: 6.3 ± 1.7 μM) and of PC12-wt (EC50: 3.8 ± 1.3 μM); this effect was not altered by the P2Y1 antagonist MRS 2216 (1 μM), but abolished by P2Y12 antagonists. In perforated-patch recordings, ADP inhibited IM relaxation amplitudes of PC12-P2Y1 cells with half-maximal effects at 2.0 ± 1.8 μM, but in PC12-wt no such effect was observed. In PC12P2Y1, but not in PC12-wt cells, ADP (1-100 μM) caused transient increases in outward currents determined at -30 mV in the perforated-patch, but not the whole-cell mode. ADP-induced currents had reversal potentials between -80 and -90 mV which was close to the calculated K+ equilibrium potential (-89 mV). Replacement of 100 mM extracellular Na+ by K+ shifted the reversal potential of ADPinduced currents to about -10 mV which was again close to the K+ equilibrium potential (-17 mV). ADP-induced currents were prevented by thapsigargin (1 μM) and by the phospholipase C inhibitor U73122 (3 μM), but not by an inactive analogue. Finally, the ADP-induced currents were significantly reduced by 100 nM apamin.